Myocardial infarction is the major pathological killer in America, resulting in the deaths of more than 500,000 persons each year. Despite important advances which have been made in preventing and treating atherosclerotic cardiovascular disease, coronary artery impairments continue to constitute a major health problem. Significant numbers of afflicted individuals who are not candidates for either bypass surgery or angioplasty as therapeutic procedures for the treatment of myocardial ischemia will benefit from a technique for accomplishing direct revascularization. A non-divergent laser beam located at the distal tip of a subcutaneous catheter would provide an operator with the critical control needed to create precise cylindrical channels in the wall of the left ventricle, without opening the chest cavity. Spire proposes to accomplish this task by using arrays of AlGaAs lasers, configured as one centimeter bars, to pump a miniature Er:YLF laser, emitting at the 2800 nm water absorption band. A catheter housing will be designed that places the miniature Er:YLF laser, on the order of one centimeter long, at the tip of the catheter; pumping energy will be conveyed to the tip via a glass optical fiber. Spire presently produces diode laser arrays featuring power levels of 2500 W/cm, sufficient for performing tissue ablation. An optical integrator will couple the optical energy from the diode laser bar into the circular fiber. The proposed effort will establish conditions, including spectral watching and input/output coupling for maximum energy transfer for effectively coupling the output flux from an array of laser diodes into the fundamental mode volume of the solid-state laser. Preliminary effects on porcine myocardial tissue samples will be evaluated.